From time to time in different projects you can still get an error when the .NET AJAX framework fails to load it's script files, it can look something like this:
http://mySite.localhost/Page-missing/?404;http://mySite.localhost:80/ScriptResource.axd?d=cX-HxJNNFFwiICal1e9E3Fltyiuue3KJiBAKoFQ2em7CnJSOyiZ3kqEwPAe3s3jFu-pwCNTI4A-GcF4jKuNyshBul05bL4FvWIGJwsE2JnB5FrGfSImgZUrdemyV5ODBNtHvYiUtxb1ZSZunFsb8UDs8Y4Mdu_fdnhJw6VNkv1oIqasV0&t=5c2f384e 404 (Not Found)
Uncaught Error: ASP.NET Ajax client-side framework failed to load.
If you are, then you are probably missing a handler setting in your web.config file
It should look like this in IIS7 (and above)
<add name="ScriptResource" verb="GET,HEAD" path="ScriptResource.axd" type="System.Web.Handlers.ScriptResourceHandler, System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" preCondition="integratedMode" />
The ScriptResource.axd is used by the Microsoft .NET AJAX framework to render helper scripts for it's UpdatePanel controls.
